Injector corrosion isolation seal

ABSTRACT

A fluid injector includes a valve assembly constructed and arranged to control flow of fluid from an inlet to an outlet of the injector. A metal housing surrounds at least a portion of the valve assembly. A plastic body is molded over at least a portion of the housing. A distal end of the body defines an integral stepped portion extending from the body. A carrier surrounds at least the distal end of the body. A seal member is in contact with at least the stepped portion and a surface of the carrier to prevent liquid from entering a space between the housing and the body.

This application claims priority from U.S. Provisional Patent Application No. 61/900,718, filed on Nov. 6, 2013, the content of which is hereby incorporated by reference into this specification.

FIELD

The invention relates generally to a seal of a fluid injector for a Reductant Delivery Unit (RDU) and, more particularly, to an improved seal used for preventing corrosion in the injector.

BACKGROUND

With reference to FIG. 1, a typical fluid injector 10 configured as an RDU employs a plastic body 20 molded over a metallic housing 44. These components reside in an area shown by arrow 11 where liquids from the environment may pool, such as rainwater and saltwater. Saltwater is known to be very corrosive and capable of shorting electrical components due to its ionic nature. Differing thermal expansion rates of the molded plastic body 20 and the metallic housing 44 creates gaps that allow pooled liquids to be drawn past O-ring 50 into the interior of the injector (between housing 44 and body 20), since the O-ring 50 seals only between the metal housing 44 and a carrier 56. Subsequent corrosion and electrical shorting may render the injector inoperable.

Accordingly, there exists a need for an improved seal that in an injector that prevents exposure of vulnerable metal components to corrosive liquids.

SUMMARY

An objective of the invention is to fulfill the need referred to above. In accordance with the principles of an embodiment, this objective is achieved by a fluid injector that includes a valve assembly constructed and arranged to control flow of fluid from an inlet to an outlet of the injector. A metal housing surrounds at least a portion of the valve assembly. A plastic body is molded over at least a portion of the housing. A distal end of the body defines an integral stepped portion extending from the body. A carrier surrounds at least the distal end of the body. A seal member is in contact with at least the stepped portion and a surface of the carrier to prevent liquid from entering a space between the housing and the body.

In accordance with another aspect of an embodiment, a method seals a fluid injector. The injector has a metal housing surrounding at least a portion of a valve assembly; a plastic body molded over at least a portion of the housing; and a carrier surrounding at least a distal end of the body. The method provides a stepped portion integral with the distal end of the housing. The stepped portion and a portion of the carrier are engaged with a seal member to prevent liquid from entering a space between the housing and the body.

Other objectives, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which:

FIG. 1 is a cross-sectional view of an conventional fluid injector for use as an RDU;

FIG. 2 is a cross-sectional view of a fluid injector, for use in as an RDU, having an improved corrosion isolation seal according to an embodiment of the present invention;

FIG. 3 is an enlarged view of the enclosed portion 3 of FIG. 1; and

FIG. 4 is a sectional view of a portion of a fluid injector having an improved corrosion isolation seal, according to an alternate embodiment of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

With reference to FIG. 2, a fluid injector according to an embodiment of the present invention is shown, generally at 10′. The injector 10′ includes an inlet cup structure, shown generally at 12, having a cup tube 14, and an inlet cup 16. The cup tube 14 can be connected to a source of reductant when the injector is configured as an RDU of a Selective Catalytic Reduction (SCR) system of a vehicle. The inlet cup 16 is connected to a shield 18, and the shield 18 substantially surrounds part of a plastic body 20 having a connector 22.

A portion of an inlet tube 24 is disposed within the body 20. A primary seal member 26, such as an elastomer O-ring, surrounds part of the inlet tube 24 so as to provide a seal between the inlet tube 24, the inlet cup 16, and the body 20.

The fluid injector 10′ has a fluid inlet 28 at an upstream end of the injector, a fluid outlet 30 at a downstream end of the injector, and a fluid passageway 32 extending from the fluid inlet 28 to the fluid outlet 30. The injector 10′ is of the conventional, solenoid-operated type, having an armature 34 operated by a coil 36 disposed on a plastic bobbin 37. Electromagnetic force is generated by current flow from the electronic control unit (not shown) through the coil 36. Movement of the end 38 of the armature 34 either separates end 38 from or contiguously engages end 38 with seat 40. When the coil 36 is energized, the end 38 of the armature 34 moves toward a fixed pole piece 42 so as to be lifted off the injector valve seat 40 to allow pressurized fluid to exit the outlet 30 of the injector 10′ in the conventional manner. The pole piece 42, armature 34 and coil 36 can be considered to be part of a valve assembly, generally indicated 43, that controls fluid flow from the fluid inlet 28 to the fluid outlet 30.

As best shown in FIG. 3, a metal housing 44 at least partially surrounds the coil 36 and bobbin 37 and a part of the armature 36. The housing 44 is overmolded by the plastic body 20. A distal end of the housing 44 includes a flange 46 for holding the seal member 50. In accordance with an embodiment, a stepped portion, preferably in the form of a bead 48 is integral with and extends from the distal end of the body 20 so as to be spaced from the flange 46. The bead 48 has a curved or rounded surface 49. A secondary seal member 50, such as an elastomer 0-ring, surrounds the lower porting of the housing 44 and provides a seal in contact with an outer surface 52 of the housing 44, the surface 49 of the bead 48, and an inner surface 54 of a carrier 56. The carrier 56 surrounds the lower or distal end of the housing and is connected to the lower portion of the shield 18.

The secondary seal member 50, with a portion being compressed against the bead 48, substantially reduces or eliminates the ability for liquid, shown generally at 58, that may enter openings 59 in the shield 18 to migrate into the space, shown generally at 60, between the outer surface 52 of the housing 44 and the inner surface 62 of the body 20.

An alternate embodiment of the injector 10″ is shown in FIG. 4, with like numbers referring to like elements. In this embodiment, the stepped portion is defined as an extension 48′ integral with the body 20 that extends from the body 20 down to the flange 46. The secondary seal member 50 provides a radial seal sandwiched between the planar surface 49′ of the extension 48′ and an inner surface 54 of the carrier 56 to eliminate the ability for liquid 58 migrate into the space 60.

Thus, the stepped portions 48, 48′ that abut with the metal housing 44 substantially eliminate the possibility of RDU injector corrosion and subsequent failure by isolating the vulnerable portion of fuel injector from the external environment. The embodiments allow for normal expansion and contraction of the O-ring 50 due to heat and swelling without overfilling the O-ring gland, which could cause O-ring failure.

The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention. 

What is claimed is:
 1. A fluid injector comprising: a valve assembly constructed and arranged to control flow of fluid from an inlet to an outlet of the injector, a metal housing surrounding at least a portion of the valve assembly, a plastic body molded over at least a portion of the housing, a distal end of the body defining an integral stepped portion extending from the body, a carrier surrounding at least the distal end of the body, and a seal member in contact with at least the stepped portion and a surface of the carrier to prevent liquid from entering a space between the housing and the body.
 2. The injector of claim 1, wherein the valve assembly includes a coil, a pole piece, and an armature movable with respect to the pole piece.
 3. The injector of claim 1, wherein the stepped portion is in the form of a bead having a curved surface, the seal member engaging in the curved surface.
 4. The injector of claim 1, wherein the seal member contacts the stepped portion, a portion of the housing, and the surface of the carrier.
 5. The injector of claim 1, wherein the stepped portion abuts with the metal housing.
 6. The injector of claim 1, wherein the seal member is sandwiched between a planar surface of the stepped portion and the surface of the carrier to define a radial seal.
 7. The injector of claim 1, wherein a distal end of the housing includes a flange for holding the seal member, the flange being spaced from the stepped portion with the seal member disposed between the flange and the stepped portion.
 8. The injector of claim 6, wherein a distal end of the housing includes a flange for holding the seal member, the stepped portion extending to the flange.
 9. The injector of claim 1, wherein the seal member is an elastomer O-ring.
 10. The injector of claim 7, wherein the seal member is an elastomer O-ring.
 11. The injector of claim 1, wherein the injector is configured as a Reductant Delivery Unit in a Selective Catalytic Reduction system and further comprises shield surrounding a portion of the body and of the carrier, the shield having openings therein.
 12. A method of sealing a fluid injector, the injector having a metal housing surrounding at least a portion of a valve assembly, a plastic body molded over at least a portion of the housing, and a carrier surrounding at least a distal end of the body, the method comprising: providing a stepped portion integral with the distal end of the housing, and engaging the stepped portion and a portion of the carrier with a seal member to prevent liquid from entering a space between the housing and the body.
 13. The method of claim 12, wherein the engaging step includes engaging an O-ring as the seal member.
 14. The method of claim 12, wherein the stepped portion is provided in the form of a bead having a curved surface, the seal member engaging in the curved surface.
 15. The method of claim 12, wherein the engaging step further includes engaging the seal member with a portion of the housing.
 16. The method of claim 12, wherein the engaging step includes sandwiching the seal member between a planar surface of the stepped portion and the surface of the carrier to define a radial seal.
 17. The method of claim 12, wherein a distal end of the housing includes a flange for holding the seal member, the flange being spaced from the stepped portion and wherein the engaging step includes disposing the seal member between the flange and the stepped portion so that the seal member engages the stepped portion.
 18. The method of claim 16, wherein a distal end of the housing includes a flange for holding the seal member, the stepped portion being provided to extend to the flange.
 19. The method of claim 17, wherein the wherein the engaging step includes engaging an O-ring as the seal member.
 20. The method of claim 12, further comprising: employing the injector as a Reductant Delivery Unit in a Selective Catalytic Reduction system of a vehicle. 